This invention relates to chelation resins and to a process for preparing chelation resins. In particular, this invention relates to novel aminopropionic acid chelation resins and processes for the preparation thereof.
A commercially employed process for preparing chelation resins involves reacting a crosslinked polymer containing pendant --CH.sub.2 Cl moieties with hexamethylenetetraamine. The resulting adduct is then hydrolyzed to form a primary methylene amine group, i.e., --CH.sub.2 NH.sub.2. This primary amine group is then further reacted with two equivalents of an .omega.-halocarboxylic acid to form the corresponding aminodicarboxylic acid moiety. Unfortunately, large amounts of waste materials are formed in the foregoing process. In the hydrolysis step, for example, six moles of formaldehyde and three moles of ammonium chloride are formed for each mole of primary amine which is formed. Such formaldehyde and ammonium chloride moieties either must be disposed of or reacted to regenerate hexamethylenetetraamine. However, even the regeneration of hexamethylenetetraamine from formaldehyde and ammonium chloride creates large amounts of salts which must be disposed of. The disposal of such undesirable side products is both an environmental and economic disadvantage of the foregoing process.
Accordingly, it would be desirable to provide a process for preparing chelation resins, which process provides for the attachment of chelating groups to a polymer backbone in good yield and without the formation of large quantities of undesired by-products.